dateMenu: Use desktop action to open Evolution calendar

We include a private hidden .desktop file for evolution's calendar
component, so that we can explicitly open that component when
evolution is configured as the default calendar application.

That's because the evolution developers didn't want to ship
additional .desktop files at the time, but they have since
then included a desktop action that can be used for the same
purpose.

Part-of: <https://gitlab.gnome.org/GNOME/gnome-shell/-/merge_requests/2479>